(a) Field of the Invention
The present invention relates to an active roll control system (ARCS) of a vehicle. More particularly, the present invention relates to an ARCS that can perform active roll control on a stabilizer bar with both ends mounted on a suspension arm by stabilizer links, respectively.
(b) Description of the Related Art
In general, the suspension system of a vehicle is a system that improves a vehicle riding comfort without damaging a vehicle and freight by controlling vibration or impact applied to an axle from the ground while the vehicle travels to prevent direct transmission to the vehicle body, by connecting the axle with the vehicle body.
The suspension system includes a chassis spring that attenuates impact from the ground, a shock absorber that improves vehicle riding comfort by attenuating free vibration of the chassis spring, and a stabilizer bar that suppresses rolling of a vehicle.
The stabilizer bar has both straight portions fixed to a vehicle body and both ends fixed to a lower arm or a strut bar by stabilizer links. Therefore, the stabilizer bar does not operate when left and right wheels move up/down together, but suppresses roll of a vehicle using a torsional elastic force while twisting when the left and right wheels move up/down, thereby performing an anti-roll function. In other words, the stabilizer bar maintains a stable position of a vehicle by inclining outward from a vehicle body due to a centrifugal force when the vehicle turns, or by using a torsional elastic force due to twisting when the left and right wheels have a relative phase difference due to bumping or rebounding while the vehicle travels.
However, the stabilizer bar may not ensure stability in turning under various conditions, using only the torsional elastic force because the stiffness is constant, such that an active roll control system that can perform active roll control by connecting an actuator such as a hydraulic cylinder or a motor to an end of the stabilizer has been developed and used in recent years.
The active roll control system of the related art has a mechanism that changes torsional stiffness of the stabilizer bar by varying the connection position with the actuator such as a hydraulic cylinder or a motor at the connecting portion of the stabilizer bar that connects the suspension arm and the end of the stabilizer bar to change the connection distance between the end of the stabilizer bar and the suspension arm. Further, a plurality of members are connected to the connecting portion by a ball joint to allow for free rotation within a predetermined range.
FIG. 1 is an exemplary view of a suspension system for a vehicle equipped with an active roll control system according to the related art and FIG. 2 is an exemplary plan view of a lower arm with the active roll control system according to the related art.
Referring to FIGS. 1 and 2, an active roll control system according to the related art actively improves a roll behavior of a vehicle by changing the stiffness of a stabilizer bar 1 based on the traveling conditions of the vehicle. The active roll control system of the related art includes a stabilizer bar 1, stabilizer links 3, and a sliding unit 5 and an actuator 6 disposed on a lower arm 7, which is a suspension arm.
Both ends of the stabilizer bar 1 are disposed on a bracket 13 on a vehicle body side subframe 11 via a mounting bush 15. The upper ends of the stabilizer links 3 are connected to an end of the stabilizer 1 by a ball joint BJ. The sliding unit 5, disposed at a side of the lower arm 7 through a housing 21, is driven by a motor 27, which is the actuator 6, to move straight connectors 25 connected with the lower ends of the stabilizer links 3 in the vehicle width direction along rail plates 23 within the housing 21.
The sliding unit 5 includes the housing 21, the rail plates 23, the connectors 25, and a cover 29 while the driving source 6 is operated by the motor 27 with a lead screw 39 as a rotary shaft. In particular, the housing 21 is formed in a rectangular box shape with the top open and fastened to a side of the lower arm 7. An extender 33 is formed at an outer end of the housing 21 and connected to a side of the lower portion of a knuckle 17 by a ball joint BJ. The rail plates 23 are arranged in the vehicle width direction within the housing 21.
Furthermore, the motor 27, the driving source 6, is fastened to an inner end of the housing 21, with the screw shaft 39, which is the rotary shaft, arranged along the rail plates 23 through the inner side of the housing 21. The connectors 25 are disposed between the rail plates 23 within the housing 21 in mesh with the screw shaft 39. The connectors 25 are connected with the lower ends of the stabilizer links by a ball joint BJ. The cover 29 has a slot formed on the cross-section as large as the operation range of the connectors 25 and is fastened to the open top of the housing 21.
The active roll control system adjusts the connection positions of the stabilizer links 3 on the lower arm 7 by driving the motor 27 based on the traveling conditions of a vehicle.
Accordingly, a lever ratio of the stabilizer links 3 changes and the stiffness of the stabilizer 1 correspondingly changes to actively control the roll strength of the vehicle.
As shown in FIG. 2, however, the active roll control system of the related art is offset OS in planes defined by connecting points P1, P2, and P3 on the lower arm and creates motion. However, in such a configuration, as actual bump rebound of a vehicle is implemented, the plane moves in the height direction of the vehicle and compliance influences the actual behavior due to the offset OS. In other words, in terms of the motor 27 that is the actuator 6, the stabilizer links 3 are required to move out of the behavior range of the vehicle, requiring a substantially large force. Further, when the lower arm 7 bumps or rebounds, the motion is included in the behavior range, and thus a substantially large load is applied since the lower ends of the stabilizer links 3 need to be moved in the vehicle width direction during the bump or rebound motion. In particular, the point P1 is usually within the range close the wheel center and the operation is generated out of the range, causing a decreased lateral force property.
Further, the motor 27 is disposed at the position with a substantially large influence by chipping due to vibration, foreign substance such as a stone, and on the like, potentially influencing the durability of the motor.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.